velocity function

Streamflow velocity estimation

Estimate streamflow velocity in average over the catchment.

velocity(hl, ...)

## Default S3 method:
velocity(hl, lagtime, method = "loire2016", ...)

## S3 method for class 'units'
velocity(hl, lagtime = NULL, method = "loire2016", ...)

## S3 method for class 'stars'
velocity(hl, ...)

## S3 method for class 'transfR'
velocity(hl, ...)

Arguments

• hl: hydraulic length of class stars, matrix, vector or transfR. If no unit is provided, hl is assumed to be in [m].
• ...: further arguments passed to or from other methods
• lagtime: lag time of the catchment. If no unit is provided, lagtime is assumed to be in [h].
• method: character string describing the method to estimate the velocity. One of "loire2016" (default), "brittany2013" or "lagtime" (see details).

Returns

A numeric value of class units, or if hl is a transfR object, the same transfR object incremented by the "uc" attribute.

Details

Estimate the average streamflow velocity of the catchment from three different approaches. Method "lagtime" estimates the velocity from the ratio between the mean hydraulic length and the lag time of the catchment. Method "loire2016" estimates the velocity from a regression based on hydraulic length only:

where $a=4.38e-4$ and $b=0.69$ have been calibrated over the Loire river basin \insertCite deLavenne2016transfR. Method "brittany2013" used a similar regression calibrated for the French Brittany region where $a=8.59e-4$

and $b=0.61$ \insertCite deLavenne2013transfR.

Examples

data(Oudon)
velocity(Oudon$hl[[1]], method = "loire2016")

object <- as_transfr(st = Oudon$obs, hl = Oudon$hl)
object <- velocity(object)
object$uc

References

\insertRef deLavenne2013transfR

\insertRef deLavenne2016transfR